Problem with weight painting
Bones affect the mesh based on their proportional weight on each vertex. The influence for each bone is calculated by dividing that bone's weight by the total weight of all bones affecting that vertex. So if the weights of all the bones add to one, then the bone influence will be the same as the weight, whcih makes things easier to reason about (the normalise function in blender will make all the bone weights sum to one).

For example if vertex 1 has the following weights:


Bone1 : 0.5
Bone2 : 1
Bone3 : 0.5


Then Bone1 has an influence of 0.25 (0.5 / (0.5 + 1 + 0.5)).

In your case you only have one bone affecting the vertex so the influence of that bone will always be one.